Workpiece positioning device positioning workpiece at two reference surfaces

ABSTRACT

A workpiece positioning device ( 1 ) includes a first positioning block (Bx) positioning one surface of a workpiece at a first reference surface in a first direction, two second positioning blocks (By 1 , By 2 ) positioning a different surface of the workpiece at a second reference surface in a second direction, seat blocks (Bz 1 , Bz 2 , Bz 3 ) positioning the workpiece in a third direction perpendicular to the first direction and the second direction, a push cylinder ( 30 ) pressing the workpiece in one direction toward an intersection line between the first and the second reference surface, a first unit ( 10 ) contacting with the one surface of the workpiece and correcting a posture of the workpiece before the first positioning block contacts with the workpiece, and a second unit ( 20 ) contacting with the different surface of the workpiece and correcting the posture of the workpiece before the second positioning blocks contact with the workpiece.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a workpiece positioning device used inpositioning a workpiece at two different reference surfaces.

2. Description of Related Art

In some cases, at the time of machining a workpiece by a machine tool,the workpiece is pressed against two different reference surfaces to bepositioned. Japanese Laid-open Patent Publication No. 5-050351 disclosesthat after a workpiece is placed on a Z-axis reference surface, theworkpiece is pressed against an X-axis reference surface by using anX-axis cylinder, and then pressed against a Y-axis reference surface byusing a Y-axis cylinder to three-dimensionally position the workpiece.

However, when a workpiece has a special shape, there is a possibilitythat pressing the workpiece against a reference surface causesrotational movement of the workpiece, and as a result, the workpiece maynot be pressed perpendicularly against the reference surface. In such acase, the workpiece is held with a clearance formed between theworkpiece and the reference surface, and the workpiece may not beprecisely set in a machining jig.

The present invention has been made in view of such circumstances, andhas an object to provide a workpiece positioning device capable ofpositioning a specially-shaped workpiece simultaneously at two differentreference surfaces.

SUMMARY OF THE INVENTION

In order to accomplish the above-described object, according to a firstaspect, there is provided a workpiece positioning device including: afirst positioning block that forms a first reference surface in a firstdirection and positions one surface of a workpiece at the firstreference surface; two second positioning blocks that form a secondreference surface in a second direction and position a different surfaceof the workpiece at the second reference surface; at least one seatblock that positions the workpiece in a third direction perpendicular tothe first direction and the second direction; a push cylinder thatpresses the workpiece in one direction toward an intersection linebetween the first reference surface and the second reference surface; afirst unit that, before the first positioning block contacts with theworkpiece, contacts with the one surface of the workpiece at frictionlower than that of the first positioning block and corrects a posture ofthe workpiece; and a second unit that, before the second positioningblocks contacts with the workpiece, contacts with the different surfaceof the workpiece at friction lower than that of the second positioningblocks and corrects the posture of the workpiece.

According to a second aspect, in the first aspect, the first unitincludes at least one pair of first rollers that contact with theworkpiece, the first positioning block is arranged between the at leastone pair of first rollers, the at least one pair of first rollers areeach pressed in the first direction toward the workpiece by an elasticmember, the second unit includes at least one pair of second rollersthat contact with the workpiece, the at least one pair of second rollersare arranged between the two second positioning blocks, and the at leastone pair of second rollers are each pressed in the second directiontoward the workpiece by an elastic member.

According to a third aspect, in the first aspect, a ball is arranged ata distal end of the push cylinder.

According to a fourth aspect, in the first aspect, the first unitincludes one pair of first contacting members that contact with theworkpiece, the first positioning block is arranged between the one pairof first contacting members, the one pair of first contacting membersare each pressed in the first direction toward the workpiece by anelastic member, the second unit includes second contacting members thatcontact with the workpiece, the second contacting members are arrangedbetween the two second positioning blocks, and the second contactingmembers are each pressed in the second direction toward the workpiece byan elastic member.

Based on the detailed description of the representative embodiments ofthe present invention illustrated in the accompanying drawings, theobject, feature, and advantageous effect, and other objects, features,and advantageous effects will be more apparent.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is an elevational view of a workpiece positioning device based ona representative embodiment of the present invention;

FIG. 2 is an enlarged view of a workpiece;

FIG. 3 is a flowchart illustrating operation of the workpiecepositioning device based on the representative embodiment of the presentinvention;

FIG. 4 is a first view illustrating relation between positioning blocksand the workpiece;

FIG. 5 is a second view illustrating relation between positioning blocksand the workpiece;

FIG. 6 is a first view for describing operation of the workpiecepositioning device in the present invention;

FIG. 7 is a second view for describing operation of the workpiecepositioning device in the present invention;

FIG. 8 is an elevational view of a workpiece positioning device based ona different embodiment of the present invention; and

FIG. 9 is an elevational view of a workpiece positioning device based onan additionally different embodiment of the present invention.

DETAILED DESCRIPTION

In the following, an embodiment of the present invention is describedwith reference to the accompanying drawings. In the following drawings,the same reference symbols are attached to the same members. In order tofacilitate understanding, reduction scales of these drawings areappropriately changed.

FIG. 1 is an elevational view of a workpiece positioning device based ona representative embodiment of the present invention. As illustrated inFIG. 1, a workpiece positioning device 1 includes a first positioningblock Bx that forms a first reference surface S1 perpendicular to an Xdirection, and two second positioning blocks By1 and By2 that form asecond reference surface S2 perpendicular to a Y direction.

Further, the workpiece positioning device 1 includes at least one seatblock among seat blocks Bz1 to Bz3, the seat block positioning aworkpiece W in a Z direction. These three seat blocks Bz1 to Bz3 form aZ-direction reference surface (not illustrated in the drawing)perpendicular to the Z direction.

In FIG. 1, the three seat blocks Bz1 to Bz3 are arranged in a shape ofan approximately right-angled triangle. The positional relation of thethree seat blocks Bz1 to Bz3 corresponds to a shape of the workpiece W,described below. It is assumed that these seat blocks Bz1 to Bz3 and thefixing blocks Bx, By1, and By2 are located at fixed positions, andfriction coefficients of the surfaces of them are relatively large.

FIG. 2 is an enlarged view of the workpiece. The workpiece W illustratedin FIG. 2 has an approximately L-shaped section, and includes flatworkpiece side surfaces F1 and F2 that are perpendicularly adjacent toeach other, and a curved side surface F3 that is connected to theseworkpiece side surfaces F1 and F2 and is curved inwards. As understoodfrom FIG. 2, the workpiece W has a shape that is line symmetry withrespect to a bisector of an angle made by the workpiece side surfaces F1and F2. It is assumed that an end surface of the workpiece W is flat.

The workpiece positioning device 1 based on the present invention isused for positioning the workpiece side surfaces F1 and F2 of theworkpiece W at the first reference surface S1 and the second referencesurface S2, respectively. Accordingly, as long as the workpiece W hasthe workpiece side surfaces F1 and F2 that are perpendicularly adjacentto each other, the workpiece W may have a different shape.

Alternatively, the workpiece side surfaces F1 and F2 may be adjacent toeach other so as to make an angle other than a right angle. In thiscase, the blocks Bx, By1, and By2 are arranged such that the firstreference surface S1 and the second reference surface S2 have the sameangle as the angle of the workpiece side surfaces F1 and F2. In thefollowing, description is made on the assumption that the workpiece sidesurfaces F1 and F2 are perpendicular to each other.

With reference to FIG. 1 once more, the workpiece positioning device 1includes a first correcting unit 10 that corrects a posture of theworkpiece W. As understood from FIG. 1, the first correcting unit 10 isarranged on the opposite side of the workpiece W with respect to thefirst reference surface S1. In other words, the first positioning blockBx is arranged between the first correcting unit 10 and the workpiece W.

As illustrated in FIG. 1, the first correcting unit 10 includes a firstbase 11, two post members 12 a and 12 b extending from the first base 11toward the workpiece W, and a common pressing member 13 attached todistal ends of the post members 12 a and 12 b. As understood from FIG.1, at a distal end of the pressing member 13, two first rollers 15 and16 are attached so as to be freely rotatable. Rotational axes of the twofirst rollers 15 and 16 are in parallel with the Z direction.

As illustrated in FIG. 1, a concave part 13 a larger than the firstpositioning block Bx is formed at the pressing member 13 of the firstcorrecting unit 10. For this reason, even when the pressing member 13approaches the workpiece W as closely as possible, the pressing member13 does not interfere with the workpiece W.

At the post members 12 a and 12 b, elastic members, e.g., springs 14 aand 14 b, are attached respectively. Accordingly, by the springs 14 aand 14 b, the pressing member 13 is pressed toward the workpiece sidesurface F1 of the workpiece W. For this reason, in an initial state inwhich the workpiece W does not exist, the distal ends of the firstrollers 15 and 16 are located at more workpiece-side positions than thefirst reference surface S1 (more right-side positions than the firstreference surface S1).

Further, the workpiece positioning device 1 includes a second correctingunit 20 that corrects a posture of the workpiece W. As understood fromFIG. 1, the second correcting unit 20 is arranged on the opposite sideof the workpiece W with respect to the second reference surface S2. Thesecond correcting unit 20 is arranged between the two second positioningblocks By1 and By2.

As illustrated in FIG. 1, the second correcting unit 20 includes asecond base 21, two post members 22 a and 22 b extending from the secondbase 21 toward the workpiece W, and a common pressing member 23 attachedto distal ends of the post members 22 a and 22 b. As understood fromFIG. 1, at a distal end of the pressing member 23, second rollers 25 and26 are attached so as to be freely rotatable. Rotational axes of the tworollers 25 and 26 are in parallel with the Z direction.

At the post members 22 a and 22 b, elastic members, e.g., springs 24 aand 24 b, are attached respectively. Accordingly, due to the springs 24a and 24 b, the pressing member 23 is pressed toward the workpiece sidesurface F2 of the workpiece W. For this reason, in the initial state inwhich the workpiece W does not exist, the distal ends of the secondrollers 25 and 26 are located at the more workpiece-side positions thanthe second reference surface S2 (more upper-side positions than thesecond reference surface S2).

Further, as illustrated in FIG. 1, the workpiece positioning device 1includes a push cylinder 30 that presses the workpiece W in onedirection. The push cylinder 30 includes a cylinder 31, a rod 32inserted into the cylinder 31, and a head 33 attached to a distal end ofthe rod 32. The cylinder 31 expands and contracts the rod 32 by afluid-pressure type or different mechanism. At a distal end of the head33, a ball roller 34 is attached so as to be freely rotatable. The ballroller 34 plays a role of smoothly pressing the workpiece W withoutdamaging the workpiece W. In the case of positioning the workpiece Whaving the shape illustrated in FIG. 1, the ball roller 34 is greatlybeneficial for pressing the curved side surface F3 of the workpiece W.

As understood from FIG. 1, the push cylinder 30 is arranged such that anaxis of the push cylinder 30 intersects with an intersection line Pbetween the first reference surface S1 and the second reference surfaceS2. For this reason, when driving the push cylinder 30, the rod 32 isexpanded so that the head 33 presses the workpiece W toward theintersection line P. The axis of the push cylinder 30 is preferablyarranged on the bisector of an angle between the first reference surfaceS1 and the second reference surface S2. Accordingly, the push cylinder30 operates so as to press the workpiece W toward both the firstreference surface S1 and the second reference surface S2,simultaneously.

FIG. 3 is a flowchart illustrating operation of the workpiecepositioning device based on the representative embodiment of the presentinvention. At the step SP1 of FIG. 3, the workpiece W is arranged at theseat blocks Bz1 to Bz3. Then, at the step SP2, the push cylinder 30 isdriven to expand the rod 32. As a result, the head 33 presses the curvedside surface F3 of the workpiece W. Thereby, the workpiece W starts tomove toward both of the first reference surface S1 and the secondreference surface S2 (step SP3).

By the way, even when the push cylinder 30 presses the workpiece W atthe step SP2, the workpiece side surfaces F1 and F2 of the workpiece Wdo not always match with the first reference surface S1 and the secondreference surface S2. This is caused by influence of positional relationbetween the positioning blocks Bx, By1, and By2 and the workpiece W, andfriction force acting between the positioning blocks Bx, By1, and By2and the workpiece W.

FIG. 4 and FIG. 5 illustrate relation between the positioning blocks andthe workpiece. For the purpose of simplicity, in FIG. 4 and FIG. 5, thefirst correcting unit 10 and the second correcting unit 20 are notillustrated. Only pressing the workpiece W by the push cylinder 30causes the workpiece W to be positioned at a location that is slightlyrotated clockwise from the first reference surface S1 and the secondreference surface S2 as illustrated in FIG. 4. In another case, asillustrated in FIG. 5, the workpiece W is positioned at a location thatis slightly rotated counterclockwise from the first reference surface S1and the second reference surface S2.

In such cases, even when the workpiece W is further pressed by using thepush cylinder 30, the workpiece W is not slid on the positioning blocksBx, By1, and By2 due to the influence of the above-described frictionforce. In other words, the push cylinder 30 alone may not correct aposture of the workpiece W.

In this regard, according to the present invention, the first correctingunit 10 and the second correcting unit 20 are arranged. The distal endsof the first rollers 15 and 16 and the second rollers 25 and 26 of thepressing members 13 and 23 of the first correcting unit 10 and thesecond correcting unit 20 are located at more workpiece-side positionsthan the first reference surface S1 and the second reference surface S2,respectively.

For this reason, when the workpiece W is pressed by the push cylinder 30to be moved at the steps SP2 and SP3, the workpiece side surface F1 ofthe workpiece W contacts with the first rollers 15 and 16 first beforecontacting with the first positioning block Bx (step SP4). In the samemanner, the workpiece side surface F2 of the workpiece W contacts withthe second rollers 25 and 26 first before contacting with the secondpositioning blocks By1 and By2 (step SP4).

The first rollers 15 and 16 and the second roller 25 and 26 contact withthe workpiece W at lower friction compared with a case of direct contactof the pressing members 13 and 23 with the workpiece W. Then, at thestep SP5, these rollers 15, 16, 25, and 26 constantly contact with theworkpiece W by biasing force of the springs 14 a, 14 b, 24 a, and 24 b,and at the same time, correct a posture of the workpiece W while movingbackward by pressing force from the workpiece W.

FIG. 6 and FIG. 7 illustrate operation of the workpiece positioningdevice in the present invention. In FIG. 6 and FIG. 7, the firstcorrecting unit 10 and the second correcting unit 20 are illustrated.FIG. 6 and FIG. 7 respectively correspond to FIG. 4 and FIG. 5 describedabove.

In the case illustrated in FIG. 6, the first roller 16 of the firstcorrecting unit 10 closer to the intersection line P, and the secondroller 26 of the second correcting unit 20 closer to the secondpositioning block By2 first contact with the workpiece W. Then, at thestep SP5, the workpiece W rotates counterclockwise while sliding on thefirst roller 16 and the second roller 26. As a result, a posture of theworkpiece W is corrected.

Further, at the step SP6, the pressing member 13 including the firstroller 16 moves backward in the left direction by the pressing forcefrom the workpiece W, and the pressing member 23 including the secondroller 26 moves backward in the downward direction by the pressing forcefrom the workpiece W.

Similarly, in the case illustrated in FIG. 7, the first roller 15 of thefirst correcting unit 10 more distant from the intersection line P, andthe second roller 25 of the second correcting unit 20 closer to thesecond positioning block By1 first contact with the workpiece W. Then,at the step SP5, the workpiece W rotates clockwise while sliding on thefirst roller 15 and the second roller 25. As a result, a posture of theworkpiece W is corrected.

Further, at the step SP6, the pressing member 13 including the firstroller 15 moves backward in the left direction by the pressing forcefrom the workpiece W, and the pressing member 23 including the secondroller 25 moves backward in the downward direction by the pressing forcefrom the workpiece W.

The ball roller 34 attached to the distal end of the push cylinder 30contacts with the curved side surface F3 of the workpiece W.Accordingly, an effect of pressing from the push cylinder 30 causes theworkpiece W to more easily move rotationally. For this reason, the ballroller 34 is useful in correcting a posture of the workpiece W at thestep SP5.

The operation of such backward movement described by using FIG. 6 andFIG. 7 causes the workpiece side surface F1 of the workpiece W tocontact with the first positioning block Bx, and causes the workpieceside surface F2 of the workpiece W to contact with the secondpositioning blocks By1 and By2 so that the workpiece W is preciselypositioned with a posture thereof being corrected (step SP7). With this,the positioning operation for the workpiece W is completed (step SP8).

Thus, according to the present invention, the first correcting unit 10and the second correcting unit 20 as well as the first positioning blockBx and the second positioning blocks By1 and By2 are used. For thisreason, even for the workpiece W of a special shape, by only pressingthe workpiece W in a single direction by the push cylinder 30, theworkpiece side surfaces F1 and F2 of the workpiece W can be preciselypositioned at the two different reference surfaces S1 and S2simultaneously. Therefore, by the workpiece positioning device 1 of thepresent invention, the workpiece W can be precisely set at a desiredmachining jig. Accordingly, generation of machining precision defect dueto a positioning error at the time of machining the workpiece W by amachining tool can be eliminated.

In FIG. 4, when the first positioning block Bx is arranged at a locationcloser to the intersection line P with the positions of the secondpositioning blocks By1 and By2 being maintained, the workpiece W moreeasily rotates clockwise. In FIG. 5, when the first positioning block Bxis arranged at a location more distant from the intersection line P withthe positions of the second positioning blocks By1 and By2 beingmaintained, the workpiece W more easily rotates counterclockwise.

In this regard, according to the present invention, the firstpositioning block Bx is arranged approximately at a center of theworkpiece side surface F1 of the workpiece W, and the two secondpositioning blocks By1 and By2 are arranged near both edge portions ofthe workpiece side surface F2 of the workpiece W, respectively. Thefirst positioning block Bx is arranged between the first rollers 15 and16. The second rollers 25 and 26 are arranged between the secondpositioning blocks By1 and By2. With such a configuration, according tothe present invention, when the workpiece W is pressed by the pushcylinder 30, the workpiece is rotationally moved so that a posturethereof can be corrected, and the workpiece W can be preciselypositioned.

By the way, FIG. 8 is an elevational view of a workpiece positioningdevice based on a different embodiment of the present invention. In FIG.8, the first rollers 15 and 16 of the pressing member 13 and the secondrollers 25 and 26 of the pressing member 23 are excluded. Instead ofthem, first contacting members 17 and 18 are attached to the pressingmember 13, and second contacting members 27 and 28 are attached to thepressing member 23. These first contacting members 17 and 18 and secondcontacting members 27 and 28 are formed of low-friction resin material,e.g., Teflon (polytetrafluoroethylene) (registered trade mark).

Further, in FIG. 8, the head 33 with the ball roller 34 is excluded. Adifferent head 35 including a hemispherical distal end is attached to adistal end of the rod 32. The head 35 does not include the ball roller34. The hemispherical distal end thereof contacts directly with thecurved side surface F3 of the workpiece W.

In the case of the different embodiment illustrated in FIG. 8, at thestep SP4 illustrated in FIG. 3, the workpiece side surface F1 of theworkpiece W contacts with the first contacting members 17 and 18 firstbefore contacting with the first positioning block Bx, and the workpieceside surface F2 of the workpiece W contacts with the second contactingmembers 27 and 28 first before contacting with the second positioningblocks By1 and By2. Then, at the step SP5, the first contacting members17 and 18 and the second contacting members 27 and 28 constantly contactwith the workpiece W by the biasing force of the springs 14 a, 14 b, 24a, and 24 b, and at the same time, correct a posture of the workpiece Wwhile moving backward by the pressing force from the workpiece W.

Accordingly, it would be apparent that even with such a configuration,the same advantageous effect as that described above can be obtained.Furthermore, in the configuration illustrated in FIG. 8, the pressingmembers 13 and 23 and the push cylinder 30 can be fabricated more simplyat a lower cost.

Further, FIG. 9 is an elevational view of a workpiece positioning devicebased on an additionally different embodiment of the present invention.The bases 11 and 21 and the pressing members 13 and 23 depicted in FIG.9 are longer than in the case illustrated in FIG. 1. In the firstcorrecting unit 10 illustrated in FIG. 9, three post members 12 a to 12c extend from the first base 11, and the pressing member 13 is attachedto distal ends of the post members 12 a to 12 c. In the same manner, inthe second correcting unit 20, three post members 22 a to 22 c extendfrom the second base 21, and the pressing member 23 is attached todistal ends of the post members 22 a to 22 c.

In addition, four rollers 19 a to 19 d whose configurations are the sameas those of the above-described first rollers 15 and 16 are attached toa distal end of the pressing member 13 so as to be freely rotatable. Inthe same manner, four rollers 29 a to 29 d whose configurations are thesame as those of the above-described second rollers 25 and 26 areattached to a distal end of the pressing member 23 so as to be freelyrotatable.

In the same manner as the representative embodiment of the presentinvention illustrated in FIG. 1, also in FIG. 9, the first positioningblock Bx is arranged between the rollers 19 a and 19 b and the rollers19 c and 19 d of the first correcting unit 10. Further, four rollers 29a to 29 d of the second correcting unit 20 are arranged between thesecond positioning blocks By1 and By2. A larger number of rollers may beattached to the correcting units 10 and 20. A configuration of the pushcylinder 30 illustrated in FIG. 9 is the same as that illustrated inFIG. 8, but may be the same as that illustrated in FIG. 1.

In the case of the additionally different embodiment illustrated in FIG.9, at the step SP4 illustrated in FIG. 3, the workpiece side surface F1of the workpiece W contacts with the rollers 19 a to 19 d first beforecontacting with the first positioning block Bx, and the workpiece sidesurface F2 of the workpiece W contacts with the rollers 29 a to 29 dfirst before contacting with the second positioning blocks By1 and By2.Then, at the step SP5, the rollers 19 a to 19 d and the rollers 29 a to29 d constantly contact with the workpiece W by biasing force of springs14 a, 14 b, 14 c, 24 a, 24 b, and 24 c, and at the same time, correct aposture of the workpiece W while moving backward by pressing force fromthe workpiece W.

Accordingly, it would be apparent that even with such a configuration,the same advantageous effect as that described above can be obtained.Further, in the configuration illustrated in FIG. 9, since a largenumber of the rollers 19 a to 19 d and 29 a to 29 d are provided, even aworkpiece W of a larger size can be precisely positioned. Furthermore,it would be understood that in the configuration illustrated in FIG. 9,a large number of the rollers 19 a to 19 d and 29 a to 29 d exist sothat the workpiece W can be slid more smoothly.

Advantageous Effects Of The Invention

According to a first aspect, even in a case of a workpiece having aspecial shape, by only pressing the workpiece in a single direction bythe push cylinder one surface and another surface of the workpiece canbe precisely positioned at the two different reference surfacessimultaneously. Accordingly, it is possible to precisely set theworkpiece in a desired machining jig, and to eliminate generation of amachining precision defect due to a positioning error when the workpieceW is machined by a machine tool.

According to a second aspect, when the push cylinder presses theworkpiece, the workpiece is rotationally moved so that a posture thereofcan be corrected, and the workpiece can be precisely positioned.

According to a third aspect, the workpiece is made to more easily moverotationally.

According to a fourth aspect, the contacting members can be simplyfabricated at a low cost.

The present invention is described above by using the representativeembodiments. However, a person skilled in the art would understand thatthe above-described modifications and various other modifications,omissions, and additions can be made without departing from the scope ofthe present invention.

What is claimed is:
 1. A workpiece positioning device comprising: afirst positioning block that forms a first reference surface in a firstdirection, and positions one surface of a workpiece at the firstreference surface; two second positioning blocks that form a secondreference surface in a second direction, and position a differentsurface of the workpiece at the second reference surface; at least oneseat block that positions the workpiece in a third directionperpendicular to the first direction and the second direction; a pushcylinder that presses the workpiece in one direction toward anintersection line between the first reference surface and the secondreference surface; a first unit that, before the first positioning blockcontacts with the workpiece, contacts with the one surface of theworkpiece at friction lower than that of the first positioning block,and corrects a posture of the workpiece; and a second unit thatcontacts, before the second positioning blocks contact with theworkpiece, with the different surface of the workpiece at friction lowerthan that of the second positioning blocks, and corrects the posture ofthe workpiece; wherein the first unit includes a first pressing member,which is pressed in the first direction toward the workpiece by anelastic member, and at least one pair of first rollers, which areattached to a distal end of the first pressing member and contact withthe one surface of the workpiece, the first positioning block isarranged between the at least one pair of first rollers, and wherein thesecond unit includes a second pressing member, which is pressed in thesecond direction toward the workpiece by an elastic member, and at leastone pair of second rollers, which are attached to a distal end of thesecond pressing member and contact with the different surface of theworkpiece, the at least one pair of second rollers are arranged betweenthe two second positioning blocks.
 2. The workpiece positioning deviceaccording to claim 1, wherein a ball is arranged at a distal end of thepush cylinder.
 3. A workpiece positioning device comprising: a firstpositioning block that forms a first reference surface in a firstdirection, and positions one surface of a workpiece at the firstreference surface; two second positioning blocks that form a secondreference surface in a second direction, and position a differentsurface of the workpiece at the second reference surface; at least oneseat block that positions the workpiece in a third directionperpendicular to the first direction and the second direction; a pushcylinder that presses the workpiece in one direction toward anintersection line between the first reference surface and the secondreference surface; a first unit that, before the first positioning blockcontacts with the workpiece, contacts with the one surface of theworkpiece at friction lower than that of the first positioning block,and corrects a posture of the workpiece; and a second unit thatcontacts, before the second positioning blocks contact with theworkpiece, with the different surface of the workpiece at friction lowerthan that of the second positioning blocks, and corrects the posture ofthe workpiece; wherein the first unit includes a first pressing member,which is pressed in the first direction toward the workpiece by anelastic member, and a pair of first contacting members, which areattached to a distal end of the first pressing member and contact withthe one surface of the workpiece, the first positioning block isarranged between the pair of first rollers, and wherein the second unitincludes a second pressing member, which is pressed in the seconddirection toward the workpiece by an elastic member, and secondcontacting members, which are attached to a distal end of the secondpressing member and contact with the different surface of the workpiece,the second contacting members are arranged between the two secondpositioning blocks.
 4. The workpiece positioning device according toclaim 3, wherein a ball is arranged at a distal end of the pushcylinder.